C O N T I N U I N G E D U C AT I O N U N I T
5
Working the
Five-Step
Felling Plan
By Ralph (Rip) Tompkins
LEARNING OBJECTIVES
tree. A hazard is defined in ISA’s Glossary of Arboricultural Terms as
“a situation or condition that may result in personal injury, property
The arborist will be able to
damage, or disruption of human activities.” Hazards can include site
h explain the five-step planning process for felling a tree
hazards, such as power lines. They can also include tree hazards, such
h discuss techniques for estimating the height of a tree for felling
as deadwood, hangers, decayed wood, vines, or animals in trees.
h explain the reactive forces that can result when using a
Obstacles are considered to be anything you can hurt or damage
chain saw
in the process of felling a tree. Obstacles may include other trees,
h plan the notch, hinge, and back cut technique for felling
people, houses, vehicles, or other personal property. It may be neca tree with lean
essary to determine the height of a tree before felling it to make sure
CEUs for this article apply to Certified Arborist, Utility Specialist,
no obstacles will be damaged.
Municipal Specialist, Tree/Worker Climber, and the BCMA practice
Determining a tree’s height helps to answer several important quescategory.
tions when creating a plan: Is it possible to fell the tree at all? Is there
enough room for it to fit? Would it fit if part of the top were removed?
A good definition of an accident is “an unplanned event.” Most
There are several techniques that can be used to determine tree height.
people don’t wake up in the morning and say, “I’m going to go out
Most techniques for height estimation are based upon a geometric printoday and get into an accident,” or “I think I’ll drop a tree across
ciple of similar right triangles. There are devices available to assist workers
some power lines.” But these things happen every day. Why?
with height estimation, such as the hypsometer and the rangefinder.
Because people sometimes fail to properly plan their tasks.
Another technique for estimating tree height employs nothing
It is especially important to use proper planning and procedures
more than a straight stick. Hold the stick so that the distance from
when felling trees. In its most basic sense, a tree felling plan is
your eye to your hand equals the distance
nothing more than taking information
from your hand to the top of the stick.
about the tree, the site, and any surroundHold your arm horizontally and the
ing hazards and obstacles, and then applystick vertically. Walk forward or backing cutting skills and other tools (e.g.,
ward until the distance from your hand
pull lines, wedges, pulleys) to bring the
to the top of the stick is proportional
tree safely to the ground. However, many
(visually equal) to the distance from the
people fail to take the time to look closely
felling cut to the top of the tree. You can
at the information available, which results
then estimate the height based on the
in far too many “unplanned events.”
distance you are standing from the tree.
Felling a tree as a whole may be the
There are some limitations to this
quickest and most profitable way to get
last method. The estimation technique
the job done, but it may not always be the
assumes that the tree is vertical, the
best way to get the job done. Before any
ground is level, and the top of the tree
cutting begins, it is important to develop
can be seen. Also, it may be necessary
a thorough plan and decide whether the
to adjust for the difference between your
tree can be safely felled at all. This article
height and the height of the felling cut.
discusses a five-step plan for tree felling.
Another good reason to determine
the height of the tree is to establish a
danger zone around the tree. Don’t assume
the tree will go exactly where you want
Any tree can pose a variety of hazards for a tree crew,
The five-step plan begins with an assess- including power lines, deadwood, hangers, decayed wood, it. One good rule of thumb is to establish
vines, and animals.
ment of hazards in, on, and around the
a circular danger zone around the tree
Step #1: Checking
for Hazards
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ARBORIST • NEWS
Devices for
determining
tree height
generally use
the principles
of geometric
triangulation.
Using a straight
stick can also
achieve an estimate of tree
height using a
geometric principle of similar
right triangles.
Find the position
at which the
distance from
your hand to
the top of the
stick visually
equals the height
of the tree from
the cut.
If you stand away from the tree at some distance in the intended
direction of fall, you can’t accurately tell whether the tree leans toward
you or away from you, but you can see whether the tree has lean
to one side or the other. This is important, because it tells you what
the good and bad sides of the tree are. The bad side is the side where
the lean is. If possible, you should finish your cutting from the
good side of the tree. That way, if something goes wrong, the tree
is more likely to fall away from you rather than toward you. It may
also be necessary to adjust your felling aim to account for side lean.
To determine forward or backward lean, stand to one side of the
tree at 90 degrees to the fall. If the tree is straight up or has backward lean, you will need something, such as a pull line or wedges,
to lift the tree over center and let gravity do the rest. If there is a lot
of back weight, you may want to add some mechanical advantage
to help pull the tree over. Generally, a forward-leaning tree does not
need a pull line because it’s already obvious which way the tree
wants to fall. If one is installed, as many company policies dictate,
there is no need to pull with excessive force. It is important that
pull lines are used properly. Excessive pre-tensioning of pull lines
can create a more dangerous cutting situation for the sawyer.
Side lean is often one of the greatest challenges in precision tree
felling. The hinge wood is strongest from front to back and weakest
from end to end. As a tree falls, the hinge begins weakening, with
the tension fibers at the back of the hinge pulling apart, and the fibers
at the front of the hinge compressing. Depending on the strength of
the wood fibers of a particular species of tree and the amount of side
lean, it may be hard for the hinge to work all the way to the ground.
Step #2: Determining the
Lean of the Tree
The lean or weight of the tree is key for several reasons. Looking
for the way a tree leans depends on the direction from which you
are looking at the tree. It is important to put yourself in the correct
position to get the correct information.
There are two types of potential leans in relation to the direction of fall. The tree may have forward or backward lean, or it may
have side lean. It is important when determining lean to take into
account the entire crown of the tree, not just the trunk. Frame the
tree with your hands on both sides of the crown, find a center spot,
and drop a plumb line down. Where the plumb line hits the ground
in relationship to the base of the tree will tell you where the lean is.
A tree with side lean can be challenging to fell, because tree species with
weak wood fiber may not hold the hinge all the way to the ground.
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C O N T I N U I N G E D U C AT I O N U N I T
with a radius (distance from the tree base to the perimeter of the
circle) that is at least 1.5 times the tree’s height. Everyone present,
except the sawyer, should be outside of this zone when a tree is
being felled.
All hazards present should be considered before continuing with
a felling plan. For example, the tree may be surrounded by houses
and may not have solid wood where the hinge needs to be. Identifying
such issues may be reason to abandon the plan at the start and seek
another means of tree removal. Once you have determined that all
identified hazards can be managed, you may move on to the next
step of the plan.
C O N T I N U I N G E D U C AT I O N U N I T
Know the characteristics of different species of wood. Some trees,
like hickory (Carya spp.), white oak (Quercus alba), and ponderosa
pine (Pinus ponderosa), have strong wood fiber and can hold the hinge
even with a heavy side lean. Others, like Tree of Heaven (Ailanthus
altissima), white pine (Pinus strobus), and many types of eucalyptus
(Eucalyptus spp.), may not fare so well with a heavy lean. If you
have more than one option of which direction to fell a tree, it is
advised that you go with the direction that has the least side lean,
because this may be the hardest factor to control.
Step #3: Establishing an
Escape Route
The third step in the plan is to establish an escape route away from
the base of the tree for when the tree begins to fall. Eighty to ninety
percent of the accidents in tree felling occur within a 15-foot (4.5 m)
radius of the tree base. Therefore, staying at the base of the tree as
it falls can increase the likelihood of an accident. The safest option
for the sawyer is to leave this area before the tree begins to fall.
Statistics show that the best escape route (path of egress) is opposite the direction of fall at a 45-degree angle. If possible, retreat on
the good side of the tree. If this is not possible, choose the next
safest direction, taking into account all hazards and obstacles. If
the desired path is obstructed (e.g., by a brush pile), clear a path
before you begin to cut.
If the information you have gathered during the first three steps,
coupled with your experience as a tree feller, signals a high degree
of probable success, then it is time to move on to the final two steps:
the notch/hinge and the back cut. If the degree of probable success
is not high, then it may be best to find another way to remove the
tree or to mitigate some of the challenges.
Step #4: The Notch/Hinge
This step involves determining which type of face notch to use and
how thick and how long to make the hinge. Contrasted with the
conventional notch or the Humboldt notch, the open-face notch of
70 degrees or greater gives you more control because it allows the
hinge to work longer. Remember, how much you want to open up
the face notch will depend on the plan for that given tree. In some
situations, such as working on a grade or felling over a sidewalk, it
may be desirable to keep the tree attached to the stump when it is
An open-face notch of 70 to 90 degrees provides more control by
allowing the hinge to work longer.
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on the ground. For other situations, a larger notch opening that
never closes might be necessary, and may only be possible when
working with more fibrous wood.
The rules of thumb for the hinge is that the hinge length should
to be at least 80 percent of the diameter of the tree, and the hinge
thickness should be no more than 10 percent (generally 7 to 10
percent) of the diameter of the tree. Again, remember that these are
not hard and fast rules and may need to be modified depending
on the situation. Is the wood fibrous, dead, or frozen? Generally,
the hinge thickness will be reduced as trees get larger and when
dealing with very dry or frozen wood.
Generally speaking, the hinge thickness should be no more than 10
percent of the tree’s diameter.
Step #5: The Back Cut
The final step in the felling plan is the back cut. How do you finish
off the cut? Remember: Face Notch + Back Cut = Hinge. It is very
important that a proper back cut is made to set up the correct hinge.
Do you use a bore cut, or cut in from the back of the tree? Do you
make the back cut level with the apex of the notch, or must you
step the back cut? Any face notch less than 70 degrees will require
a stepped back cut. A stepped back cut may be warranted even with
an open-face notch if there is a chance the tree will get hung up in
another tree.
The bore cut is the best option when dealing with trees with forward lean/weight. Use the end of the saw to bore through the tree
from the side, leaving strong holding wood (commonly known as
a strap) in the back. This will alleviate the potential for barber chair,
which is a dangerous situation that occurs when a forward-leaning
tree splits vertically up from the back cut. The bore cut will also
allow you to set up the hinge without any worry that the tree will
move. Once the hinge is set, perform a final safety check, make sure
everyone is clear of the tree, and then cut the strap, allowing the
tree to fall.
Bore cutting is a technique that can only be learned once you
understand the reactive forces of the chain saw. Cutting with the
top of the bar will cause the saw to push back towards the operator. Cutting with the bottom of the bar will pull the saw away from
the operator. If the front, upper corner of the tip of the bar comes
in contact with an object, it will cause the saw to kick back. Kickback
is a potentially dangerous reactive force that can happen seven times
faster than a human can react. It is always important to be aware of
the location of the upper quadrant of the tip of the bar.
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ARBORIST • NEWS
the pull line. Wedges can be a big help to keep the tree from sitting
down on your saw or to help lift the tree over center.
Conclusion
Felling an entire tree can be a quick and profitable way to remove
a tree, but if things go wrong, it can be quite costly. The margin for
error in an urban environment is often very small. The importance
of a thorough, well-devised felling plan can’t be understated. Always
think through all the steps of the plan before beginning to cut. Sometimes it may be best to remove the tree with an alternative method.
The well-prepared arborist not only uses planning procedures to
fell a tree, but also uses planning procedures to determine when a
tree should not be felled. Felling situations that are too dangerous
or have too many undefined circumstances should not be attempted.
Safety needs to remain the top priority.
Rip Tompkins is an ISA Certified Arborist, Massachusetts Certified Arborist,
and vice president of ArborMaster Training, Inc. (Little Compton, RI). He
also is an alternate member of the ANSI Accredited Standards Committee
Z133, past chairman of the ITCC Committee, and the 1996 International
Tree Climbing Championship Master’s Champion.
Illustrations courtesy of Brian Kotwica.
Dangerous kickback occurs when the front, upper corner of the tip of
the bar on the chain saw comes in contact with an object.
CEU TEST QUESTIONS
Take your quiz online! Go to www.isa-arbor.com/certification/ceus.aspx and click on
“Arborist News Quizzes Online.” If you need a login and password, send an e-mail to
[email protected].
To receive continuing education unit (CEU) credit (1.0 CEU) for home study of this article,
after you have read it, darken the appropriate circles on the answer form of the insert card in this
issue of Arborist News. (A photocopy of the answer form is not acceptable.) A passing score for this
test requires 16 correct answers.
Next, complete the registration information, including your certification number, on the
answer form and send it to ISA, P.O. Box 3129, Champaign, IL 61826-3129. Answer forms for
this test, Working the Five-Step Felling Plan, may be sent for the next 12 months.
If you do not pass the quiz, ISA will send you a retake answer sheet. You may take the quiz
as often as necessary to pass. If you pass, you will not be notified; rather, you will see the credit
on your CEU report (available online). Processing CEUs takes 4 to 6 weeks.
CEUs for this article apply to Certified Arborist, Utility Specialist, Municipal Specialist,
Tree/Worker Climber, and the BCMA practice category.
1. According to the author, what is the most
basic element in developing a tree felling plan?
a. creating a blueprint
b. gathering information
c. using high-tech devices
d. determining a tree’s height
2. The first step in a tree felling plan is to assess
a. the estimated cost
b. the quickest way to complete the job
c. hazards
d. unplanned events
5. The danger zone around a tree base should
have a radius of
a. no more than 20 feet (6.1 m)
b. half the height of the tree
c. the exact height of the tree
d. at least 1.5 times the height of the tree
6. The “bad side” of the tree is the side where
there is lean.
a. True
b. False
7. If a solid tree is being felled toward the
north, but has a slight lean toward the east,
the “good” side of the tree will be the
a. east
b. west
c. north
d. south
3. In tree felling, obstacles are
a. hangers and deadwood
b. located with an hypsometer
c. anything that can be hurt or damaged
d. not a factor in creating a plan
8. In the example above, you would want to
finish the back cut on the
a. east side of the tree
b. west side of the tree
c. north side of the tree
d. south side of the tree
4. Determining the height of the tree to be
felled can help you
a. decide if there is enough room to fell it
b. consider alternative methods of removal
c. establish a danger zone around the tree
d. all of the above
9. All of the following are essential steps in
tree felling except
a. limbing and bucking
b. determining the lean of the tree
c. checking for hazards
d. establishing an escape route
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C O N T I N U I N G E D U C AT I O N U N I T
The bottom corner of the tip of the bar is used to initiate a bore
cut. Starting with this corner will help pull the saw into the wood.
The bore cut technique needs to be learned through proper, supervised training and practiced in low-risk situations.
Straight or back-leaning trees can be finished with a back cut,
cutting in from the rear of the tree, as long as there is proper use of
C O N T I N U I N G E D U C AT I O N U N I T
10. A stepped back cut can be warranted
a. any time the bore cut is used
b. with a hinge greater than 10 percent of
the diameter
c. with any face notch less than 70 degrees
d. any time an open-face notch is used
14. A bore cut is initiated with which part of
the chain saw?
a. upper corner of the tip of the bar
b. the top of the bar
c. bottom corner of the tip of the bar
d. the bottom of the bar
19. Which is the best cutting option when a
felling tree with a forward lean?
a. Humboldt notch
b. heading cut
c. bore cut
d. reduction cut
11. The total percentage of accidents in tree
felling that occurs within a 15-foot (4.5 m)
radius of the tree base is
a. less than 10 percent
b. 25 to 30 percent
c. 50 percent
d. 80 to 90 percent
15. Sometimes a forward-leaning tree can split
vertically up from the back cut. This creates
a dangerous situation called
a. bucking
b. barber chair
c. kickback
d. a bore cut
20. When using the bore cut technique for
making the back cut in a felling operation,
the last part to be cut is the
a. apex of the notch
b. hinge
c. strap of wood in back
d. good side of the tree
12. The best escape route during a tree felling is
a. opposite the direction of the fall at a
45-degree angle
b. opposite the direction of the fall at a
75-degree angle
c. in the direction of the fall at a 45-degree
angle
d. to the rear, directly opposite the felling
direction
16. To which degree should the open-face
notch be cut for the most control?
a. 20 to 30 degrees
b. 40 to 50 degrees
c. 60 to 65 degrees
d. 70 degrees or greater
13. Kickback occurs when an object comes in
contact with the
a. starting corner of the chain saw bar
b. front, upper quadrant of the tip of the
chain saw bar
c. sprocket of a chain saw when the saw is
at full throttle
d. depth gauge between the cutters on the
chain
17. The hinge length should be at least
a. 25 percent of the diameter of the tree
b. 50 percent of the diameter of the tree
c. 60 percent of the diameter of the tree
d. 80 percent of the diameter of the tree
18. The hinge thickness should be no more than
a. 10 percent of the diameter of the tree
b. 25 percent of the diameter of the tree
c. 40 percent of the diameter of the tree
d. 50 percent of the diameter of the tree
For more
CEUs
go to ISA’s website
(www.isa-arbor.com)
and search “Arborist
News Quizzes”
To Fell A Tree
A Complete Guide to Successful Tree Felling
and Woodcutting Methods
By Jeff Jepson, Illustrations By Bryan Kotwica
To Fell A Tree was written for the professional tree cutter as well as the weekend woodcutter. The book is filled with practical information essential to the safety and success
of any tree felling and woodcutting operation, whether the work is performed in the
forest or in the backyard. With step-by-step methods and more than 200
illustrations, topics include preparations before the work
begins, felling a tree using a three-step procedure, felling
difficult trees, and limbing and bucking the tree.
Other topics include: potential work hazards, chain saw safety,
personal protective equipment, protecting people and property,
felling storm-damaged trees, moving limbs and logs, and methods
for splitting and stacking wood.
Jepson’s To Fell A Tree is a 160-page paperback publication. #O2041 • Retail Price: $19.95 • Member Price: $17.95
To order, call 1-888-ISA-TREE or visit us online at www.isa-arbor.com/store
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